A signal driver is a circuit that receives an input signal and increases its power so that it can be properly processed by another circuit. Tri-state logic is digital logic in which there are three possible states, rather than the usual two states of digital off (0) or digital on (1). In tri-state logic there is a digital off (0) state, a digital on (1) state, and a high impedance state.
A tri-state signal driver is a signal driver that can operate in the three tri-state logic states. Prior art tri-state signal drivers may be implemented by modifying a conventional inverter. For example, a conventional inverter may be modified by adding a new PMOS transistor in series with an existing PMOS transistor of the inverter, and a new NMOS transistor in series with an existing NMOS transistor of the inverter. However, with this approach, to achieve the same drive strength of the original inverter, the new transistors must be relatively large. Thus, this implementation technique is relatively space-intensive.
Consequently, it would be highly desirable to provide an improved tri-state signal driver circuit. Such a device should use less die space than known tri-state signal driver circuits. Ideally, the device would use a conventional inverter and implement the tri-state operation through another circuit element associated with the tri-state signal driver circuit.